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ABSTRACT Using 14 years of operational data, this study compares four small grid-connected thin-film photovoltaic systems installed as twin setups in Madrid and Jaén, Spain: a-Si (0.90 kW) and a-Si/μc-Si (0.88 kW). This configuration enables a controlled comparison between a more continental climate and warmer southern Mediterranean conditions. The a-Si systems were the best performers in terms of energy production, with average annual final system yields of 1537 kWh·kW -1 in Jaén and 1438 kWh·kW -1 in Madrid, and average annual performance ratios of 0.73 and 0.71, respectively. For a-Si/μc-Si, the corresponding values were lower: 1449 and 1361 kWh·kW -1 , and 0.68 and 0.67, respectively. Jaén generally outperformed Madrid, especially in winter, due to higher irradiance levels and slightly more favourable spectral conditions. However, a-Si/μc-Si showed slightly greater long-term stability. When regular cleaning was applied only in Jaén during a subperiod, the Madrid systems exhibited a more pronounced performance decline, revealing the role of soiling-related losses. Over the full analysis period, representative performance loss rates remained moderate, ranging from about −0.75 to −0.96 %·y -1 . Overall, this study provides a rare long-term field benchmark for legacy thin-film technologies, supporting PV lifetime modelling, performance-decline assessment, and the evaluation of emerging thin-film concepts under real operating conditions.
Dias et al. (Wed,) studied this question.